1. Field of the Invention
The present invention relates to a method and apparatus for encoding and decoding multi-channel signals, and more particularly, to a method and apparatus for encoding a left-side channel signal into a first signal and encoding the combination of a left-side channel signal and a right-side channel signal into a second signal according to a similarity between channels for multi-channel signals and a decoding method and apparatus therefor.
2. Description of the Related Art
In digital audio transmission, audio signals to be transmitted are less affected by surrounding noise than conventional analog transmission and good sound quality like that obtained by using a compact disc (CD) can be obtained. However, as the amount of data to be transmitted increases, the capacity of a memory or the capacity of a transmission line should be increased accordingly.
To solve these problems, data compression technology is needed. In the case of audio compression technology, an original sound signal is compressed into a smaller amount of information, transmitted, and then decompressed such that the quality of the decompressed sound signal is nearly the same as that of the original sound signal. In other words, audio compression technology intends to play the same sound quality as the original sound and transmit a smaller amount of information.
In comparison with mono audio as an audio signal provided from one channel, stereo audio which is the combination of audio signals provided from a plurality of channels allows a listener to feel stereoscopic sound.
In a conventional method of processing audio signals such as perceptual noise substitution (PNS), audio signals can be effectively processed at a low bit rate such as 64 kbps/stereo using an MPEG-4 audio coding tool, but sound quality is degraded at a high bit rate. In the conventional method, in particular, when a transient audio signal is processed, sound quality is more degraded.
In addition, since a stereo audio signal is a combination of mono audio signals supplied from a plurality of channels, it is more difficult and expensive to store or transmit stereo audio signals. This is because, when mono audio signals supplied from the plurality of channels are encoded independently in each channel, the size of data increases by the number of channels. The size of data can be reduced by reducing a sampling rate or adopting lossy encoding. However, the sampling rate directly affects the sound quality, and lossy encoding may cause degradation of the sound quality.
As such, there is required a method of encoding and decoding multi-channel signals by which the sound quality of a digital signal and a transient signal having a high bit rate is not greatly degraded and redundant information between channels are effectively removed without affecting the sound quality of the digital signal and the transient signal.